1. Technical Field
The present invention relates to a shock absorber and a suspension apparatus effectively usable to damp vibrations of, for example, an automobile.
2. Background Art
Generally, a vehicle, such as a two-wheeled or four wheeled motor vehicle, includes a hydraulic shock absorber disposed between a wheel side and a vehicle body side, and is configured to damp, for example, vertical vibrations generated when the vehicle is running by the shock absorber. There is known one type of such a shock absorber called semi-active suspension apparatus configured to variably control a damping force (for example, refer to Japanese Patent Public Disclosure No. 2009-281584).
The semi-active suspension apparatus as a conventional shock absorber can variably control a damping force by controlling a hydraulic flow in a cylinder, thereby realizing energy conservation and a compact structure. However, the semi-active suspension apparatus cannot generate a wide range of damping forces compared to an active suspension apparatus configured to supply hydraulic fluid from the outside into a cylinder and discharge the hydraulic fluid from the cylinder to the outside, which leads to the necessity of further improvement of the semi-active suspension apparatus still now.